:root {
    --primary-color: #4e73df;
    --secondary-color: #858796;
    --success-color: #1cc88a;
    --info-color: #36b9cc;
    --warning-color: #f6c23e;
    --danger-color: #e74a3b;
    --dark-bg: #2c3e50;
}

body {
    font-family: 'Nunito', sans-serif;
    background-color: #f8f9fc;
}

#wrapper {
    display: flex;
}

#sidebar {
    min-width: 250px;
    max-width: 250px;
    min-height: 100vh;
    background: var(--dark-bg);
    color: white;
    transition: all 0.3s;
}

#sidebar .sidebar-header {
    padding: 20px;
    background: rgba(0,0,0,0.1);
    text-align: center;
}

#sidebar ul li a {
    padding: 15px 20px;
    display: block;
    color: rgba(255,255,255,0.7);
    text-decoration: none;
}

#sidebar ul li a:hover, #sidebar ul li.active a {
    color: white;
    background: rgba(255,255,255,0.1);
}

#content {
    width: 100%;
    padding: 20px;
}

.card {
    border: none;
    box-shadow: 0 0.15rem 1.75rem 0 rgba(58, 59, 69, 0.15);
    margin-bottom: 20px;
}

.card-header {
    background-color: #f8f9fc;
    border-bottom: 1px solid #e3e6f0;
    font-weight: bold;
    color: var(--primary-color);
}

.stats-card {
    border-left: 4px solid var(--primary-color);
}
.stats-card.sales { border-left-color: var(--success-color); }
.stats-card.expenses { border-left-color: var(--danger-color); }
.stats-card.balance { border-left-color: var(--info-color); }

.login-container {
    max-width: 400px;
    margin: 100px auto;
}